Update QDK to 0.15

[JakuJ]

• Bumped QDK to 0.15, bringing support for the new use and borrow keywords.
• Updated some vulnerable NPM dependencies, as per dependabot's alerts.
• Updated all .qs files (test source code, examples used by the app) to use the new syntax.
• Updated syntax highlighing in the editor (the .tmLanguage file)

Closes #113.

Edit: also registered '//' as the line comment (resolved #73).

[codecov[bot]]

Codecov Report

Merging #114 (a5f270b) into develop (306e860) will increase coverage by 0.09%. The diff coverage is 75.00%.

@@             Coverage Diff             @@
##           develop     #114      +/-   ##
===========================================
+ Coverage    95.95%   96.04%   +0.09%     
===========================================
  Files           51       51              
  Lines         1284     1291       +7     
===========================================
+ Hits          1232     1240       +8     
+ Misses          52       51       -1     

Flag	Coverage Δ
unittests	96.04% <75.00%> (+0.09%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
Compiler/EventLogger.cs	77.77% <20.00%> (+8.54%)	:arrow_up:
Compiler/AllocationTagger.cs	78.57% <100.00%> (ø)
Compiler/InMemoryEmitter.cs	89.65% <100.00%> (+0.36%)	:arrow_up:
Compiler/QsCompiler.cs	90.90% <100.00%> (+2.53%)	:arrow_up:
Simulator/InterceptingSimulator.cs	100.00% <100.00%> (ø)

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